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<b><i>txn</i> <b>commit</b></b>
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<b><pre>txn commit
	[-nosync]
	[-sync]
</pre></b>
<b>Description(txn commit)</b>
<p>The <i>txn</i> <b>commit</b> command ends the transaction.</p>
<p>In the case of nested transactions, if the transaction is a parent
transaction with unresolved (neither committed or aborted) child
transactions, the child transactions are aborted and the commit of the
parent will succeed.</p>
<p>In the case of nested transactions, if the transaction is a child
transaction, its locks are not released, but are acquired by its parent.
Although the commit of the child transaction will succeed, the actual
resolution of the child transaction is postponed until the parent
transaction is committed or aborted; that is, if its parent transaction
commits, it will be committed, and if its parent transaction aborts, it
will be aborted.</p>
<p>If the <b>-nosync</b> option is not specified, a commit log record is
written and flushed to disk, as are all previously written log records.</p>
<p>The options are as follows:</p>
<br>
<b>-nosync</b><ul compact><li>Do not synchronously flush the log. This means the transaction will
exhibit the ACI (atomicity, consistency, and isolation) properties, but
not D (durability); that is, database integrity will be maintained, but
it is possible that this transaction may be undone during recovery
instead of being redone.
<p>This behavior may be set for an entire Berkeley DB environment as part of
the <b>berkdb env</b> call.</p></ul>
<b>-sync</b><ul compact><li>Synchronously flush the log. This means the transaction will exhibit
all of the ACID (atomicity, consistency, isolation and durability)
properties.
<p>This behavior is the default for Berkeley DB environments unless the
<b>-nosync</b> option was specified to the <b>berkdb env</b> or
<i>env</i> <b>txn</b> calls.</p></ul>
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<p>After <i>txn</i> <b>commit</b> has been called, regardless of its return, the
<b>txn</b> handle may not be accessed again.  If <i>txn</i> <b>commit</b>
encounters an error, this transaction and all child transactions of this
transaction are aborted.</p>
<p>The <i>txn</i> <b>commit</b> command returns 0 on success, and in the case of error, a Tcl error
is thrown.</p>
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